In a process of implementing the technical solutions of the embodiments of the disclosure, the inventor of the disclosure at least finds the following technical problems in the prior arts.
A Multiple-Input Multiple-Output (MIMO) technology is a technology disclosed by the Bell Laboratory at the end of the last century for a multi-antenna communication system, and specifically, multiple antennae (or array antennae) and multiple channels are adopted at both a transmitter and a receiver to effectively suppress channel fading. In addition, compared with a conventional single-antenna communication system, a multi-antenna communication system adopting MIMO may increase system capacity manyfold, and may also improve channel reliability and lower an error bit rate.
An MIMO technology is divided into Single-User MIMO (SU-MIMO) and MU-MIMO), and as shown in FIG. 1, SU-MIMO refers to that there is only one piece of User Equipment (UE) on the same time-frequency resource, while MU-MIMO refers to that multiple pieces of UE occupy the same time-frequency resource. The maximum number of data streams which may be transmitted in an MIMO system may not exceed a rank of a channel estimation matrix, so that the number of UE (i.e. the number of UE which may be paired) in an MU-MIMO system is determined by the number of antennae of a NodeB side, and the total number of antennae of all the UE is required to be smaller than or equal to the number of the antenna of the NodeB side. Common-Channel Interference (CCI) between channels is eliminated by virtue of a precoding technology, so that spectrum resources are saved, and system throughput is greatly increased.
An MIMO technology is a technology mainly applied to a physical layer of a Long Term Evolution (LTE) system. A conventional LTE system mainly adopts 8 antenna ports at the NodeB side and applies to a transmission scenario of maximally supported 8 data streams mapped from two code words supported by a service channel of a Physical Downlink Shared Channel (PDSCH). An ordinary structure of a downlink physical channel is shown in FIG. 2, code words (at most two) transmitted by an upper Media Access Control (MAC) layer of a physical layer are scrambled and modulated to generate complex modulated symbols respectively, and then layer mapping is performed, through antenna ports with a mapping capability, on the complex modulated symbols generated by each code word to generate multiple layers of data streams; precoding and resource mapping are performed on each of the multiple layers of data streams; and Orthogonal Frequency Division Multiplexing (OFDM) signals are finally generated on respective antenna ports, and mapped to the corresponding antenna ports. Here, due to limited number of the code words, two pieces of UE may be paired during MU-MIMO of the LTE system.
An LTE system of Earlier Release 8 (R8) has referred to a space division multiplexing technology for multiple layers of data streams on a PDSCH, an MU-MIMO form may be supported, and Downlink Control Information (DCI) is DCI format 1D.
An LTE system of Release 9 (R9) defines transmission mode 7 (single-stream beamforming) and transmission mode 8 (multi-stream beamforming), and such two beamforming-based transmission modes under a Time Division Duplexing (TDD) mode estimate channels by virtue of DeModulation Reference Signals (DMRSs) and then perform data demodulation in an equalization manner. DCI is DCI format 2A and DCI format 1D or 2B respectively. At this moment, MU-MIMO becomes more flexible in the system, and multiple pieces of UE may identify own corresponding channels through different DMRS sequences, thereby implementing accurate channel estimation.
An LTE system of later Release 10 (R10) defines new transmission mode 9, and more DMRS ports (as many as 8 DMRS ports) are involved, so that a single piece of UE may maximally identify 8 layers of data streams. Its DCI is DCI format 2C.
As mentioned above, under the limitation of a 3rd Generation Partnership Project (3GPP) protocol, transmission mode 8 may only support a scenario where at most two pieces of UE are paired and each piece of paired UE may identify a single layer of data stream, transmission mode 9 may only support a scenario where a single piece of UE may identify at most 8 layers of data streams, and along with increase of the number of data streams, the number of DMRS ports required to be supported correspondingly increases, and the number of data Resource Elements (REs) correspondingly decreases.
Therefore, in a conventional LTE system, each cell theoretically supports data sending of only two pieces of UE on the same time-frequency resource, that is, pairing of only two pieces of UE is supported, and it is impossible to pair at least two pieces of UE on the premise of not changing any receiving flow.